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Zhiqiang Guan - One of the best experts on this subject based on the ideXlab platform.

  • experimental investigation into the positive effects of a tri blade like windbreak wall on small size natural draft dry cooling towers
    Applied Thermal Engineering, 2016
    Co-Authors: Zhiqiang Guan, Hal Gurgenci, Abdullah M Alkhedhair
    Abstract:

    Cooling efficiency of heat exchangers in conventional large natural draft dry cooling towers (NDDCTs) is often affected by crosswind. In our previous work, it was verified that the crosswind influence is more significant on short NDDCTs (height <30 m) with horizontal heat exchangers than on large towers at a same wind speed. A new tri-blade-like windbreak has been proposed in the tower base to improve the cooling performance. In this paper, a following-up experimental study on a 1:12.5 scaled NDDCT equipped with a novel round heat exchanger model is reported. Instrument measurements were made on the air temperatures and velocities as well as the heat rejection rates on the scaled cooling tower model with and without the windbreak wall, and the influences of three wind attack angles (0°, 30°, and 60°) with respect to the windbreak wall were particularly investigated. The overall heat transfer performance of the cooling tower was found sensitive to the attack angles. The study verified that the cooling performance is improved most if the tri-blade-like Windbreaks placed in the attack angle of 0°. The experiment results qualitatively agreed with the predictions of the two 3D CFD models, the 15 m-tall prototype and the 1.2 m-tall tower model.

  • the influence of windbreak wall orientation on the cooling performance of small natural draft dry cooling towers
    International Journal of Heat and Mass Transfer, 2014
    Co-Authors: Hal Gurgenci, Zhiqiang Guan
    Abstract:

    While crosswind has a negative influence on natural draft dry cooling towers (NDDCTs) of all sizes, the influence may be fatal for short towers (height < 30 m) proposed for geothermal or solar thermal power plants. In a previous paper, the authors demonstrated the potential for tri-blade-like windbreak walls not to only maintain but significantly improve the short tower cooling performance. The effect of crosswind attack angle (windbreak walls orientation) was not examined in that paper. The present paper investigates that effect for a 15 m-high small-size NDDCT with horizontally-arranged heat exchangers. 3D CFD models with different wind attack angles (0°, 10°, 20°, 30°, 40°, 50°, and 60°) are set up and computed at different crosswind speeds. The results indicate that the way the cooling tower performance varies with the crosswind speed is highly sensitive to the wind attack angles. At attack angles of 0° and 60° the cooling performance is improved by Windbreaks over the entire crosswind speed range investigated. Other attack angles lead to unfavourable effects at certain wind speeds. The differences are related to the turbulent airflow field in the tower bottom. The results suggest that the tri-blade-like Windbreaks placements always with one symmetry axis alignment with the dominant crosswind direction. The findings could be used to determine the windbreak installation angles with respect to the most frequent direction(s) of the ambient wind in a given district.

  • windbreak walls reverse the negative effect of crosswind in short natural draft dry cooling towers into a performance enhancement
    International Journal of Heat and Mass Transfer, 2013
    Co-Authors: Yuanshen Lu, Zhiqiang Guan, Hal Gurgenci
    Abstract:

    Crosswind effect on the cooling performance of large natural draft dry cooling towers (NDDCT) has been verified to be unfavourable by many researchers. Small size natural draft cooling towers (height <30 m) proposed for geothermal and other renewable power plants are expected to be more negatively affected. CFD modelling has been carried out to numerically analyse the heat transfer performance of a 15 m-high small NDDCT under different crosswind speeds. Simulations show that, at certain crosswind speeds, the crosswind significantly degrades the cooling performance. However, the negative effect of the crosswind can be turned into positive in small natural draft cooling towers by introducing windbreak walls that guide the air mobilised by crosswind through the heat exchangers. When windbreak walls are used, the results show that the tower performance improves with increased crosswind velocity.

Hal Gurgenci - One of the best experts on this subject based on the ideXlab platform.

  • experimental investigation into the positive effects of a tri blade like windbreak wall on small size natural draft dry cooling towers
    Applied Thermal Engineering, 2016
    Co-Authors: Zhiqiang Guan, Hal Gurgenci, Abdullah M Alkhedhair
    Abstract:

    Cooling efficiency of heat exchangers in conventional large natural draft dry cooling towers (NDDCTs) is often affected by crosswind. In our previous work, it was verified that the crosswind influence is more significant on short NDDCTs (height <30 m) with horizontal heat exchangers than on large towers at a same wind speed. A new tri-blade-like windbreak has been proposed in the tower base to improve the cooling performance. In this paper, a following-up experimental study on a 1:12.5 scaled NDDCT equipped with a novel round heat exchanger model is reported. Instrument measurements were made on the air temperatures and velocities as well as the heat rejection rates on the scaled cooling tower model with and without the windbreak wall, and the influences of three wind attack angles (0°, 30°, and 60°) with respect to the windbreak wall were particularly investigated. The overall heat transfer performance of the cooling tower was found sensitive to the attack angles. The study verified that the cooling performance is improved most if the tri-blade-like Windbreaks placed in the attack angle of 0°. The experiment results qualitatively agreed with the predictions of the two 3D CFD models, the 15 m-tall prototype and the 1.2 m-tall tower model.

  • the influence of windbreak wall orientation on the cooling performance of small natural draft dry cooling towers
    International Journal of Heat and Mass Transfer, 2014
    Co-Authors: Hal Gurgenci, Zhiqiang Guan
    Abstract:

    While crosswind has a negative influence on natural draft dry cooling towers (NDDCTs) of all sizes, the influence may be fatal for short towers (height < 30 m) proposed for geothermal or solar thermal power plants. In a previous paper, the authors demonstrated the potential for tri-blade-like windbreak walls not to only maintain but significantly improve the short tower cooling performance. The effect of crosswind attack angle (windbreak walls orientation) was not examined in that paper. The present paper investigates that effect for a 15 m-high small-size NDDCT with horizontally-arranged heat exchangers. 3D CFD models with different wind attack angles (0°, 10°, 20°, 30°, 40°, 50°, and 60°) are set up and computed at different crosswind speeds. The results indicate that the way the cooling tower performance varies with the crosswind speed is highly sensitive to the wind attack angles. At attack angles of 0° and 60° the cooling performance is improved by Windbreaks over the entire crosswind speed range investigated. Other attack angles lead to unfavourable effects at certain wind speeds. The differences are related to the turbulent airflow field in the tower bottom. The results suggest that the tri-blade-like Windbreaks placements always with one symmetry axis alignment with the dominant crosswind direction. The findings could be used to determine the windbreak installation angles with respect to the most frequent direction(s) of the ambient wind in a given district.

  • windbreak walls reverse the negative effect of crosswind in short natural draft dry cooling towers into a performance enhancement
    International Journal of Heat and Mass Transfer, 2013
    Co-Authors: Yuanshen Lu, Zhiqiang Guan, Hal Gurgenci
    Abstract:

    Crosswind effect on the cooling performance of large natural draft dry cooling towers (NDDCT) has been verified to be unfavourable by many researchers. Small size natural draft cooling towers (height <30 m) proposed for geothermal and other renewable power plants are expected to be more negatively affected. CFD modelling has been carried out to numerically analyse the heat transfer performance of a 15 m-high small NDDCT under different crosswind speeds. Simulations show that, at certain crosswind speeds, the crosswind significantly degrades the cooling performance. However, the negative effect of the crosswind can be turned into positive in small natural draft cooling towers by introducing windbreak walls that guide the air mobilised by crosswind through the heat exchangers. When windbreak walls are used, the results show that the tower performance improves with increased crosswind velocity.

Abdullah M Alkhedhair - One of the best experts on this subject based on the ideXlab platform.

  • experimental investigation into the positive effects of a tri blade like windbreak wall on small size natural draft dry cooling towers
    Applied Thermal Engineering, 2016
    Co-Authors: Zhiqiang Guan, Hal Gurgenci, Abdullah M Alkhedhair
    Abstract:

    Cooling efficiency of heat exchangers in conventional large natural draft dry cooling towers (NDDCTs) is often affected by crosswind. In our previous work, it was verified that the crosswind influence is more significant on short NDDCTs (height <30 m) with horizontal heat exchangers than on large towers at a same wind speed. A new tri-blade-like windbreak has been proposed in the tower base to improve the cooling performance. In this paper, a following-up experimental study on a 1:12.5 scaled NDDCT equipped with a novel round heat exchanger model is reported. Instrument measurements were made on the air temperatures and velocities as well as the heat rejection rates on the scaled cooling tower model with and without the windbreak wall, and the influences of three wind attack angles (0°, 30°, and 60°) with respect to the windbreak wall were particularly investigated. The overall heat transfer performance of the cooling tower was found sensitive to the attack angles. The study verified that the cooling performance is improved most if the tri-blade-like Windbreaks placed in the attack angle of 0°. The experiment results qualitatively agreed with the predictions of the two 3D CFD models, the 15 m-tall prototype and the 1.2 m-tall tower model.

Todd A Kellerman - One of the best experts on this subject based on the ideXlab platform.

Greg C Liknes - One of the best experts on this subject based on the ideXlab platform.

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